Home / 12.90-17.80-8.05

Finding the Fourth Proportional to 12.90, 17.80 and 8.05

Calculator

Solution

The fourth proportional to 12.90, 17.80 and 8.05 is: 11.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    12.90 : 17.80 = 8.05 : x
  2. Step 2: Convert to fraction form
    12.90/17.80 = 8.05/x
  3. Step 3: Cross multiply
    12.90x = 17.80 × 8.05
  4. Step 4: Simplify right side
    12.90x = 143.29
  5. Step 5: Solve for x
    x = 143.29/12.90
  6. Step 6: Final answer
    x = 11.11

Related Problems

Find fourth proportional to 6.45, 8.90 and 4.03
Half scale
Find fourth proportional to 25.81, 35.60 and 16.10
Double scale
Find fourth proportional to 13.90, 19.18 and 9.05
Similar ratio
Find fourth proportional to 19.35, 26.70 and 12.08
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.